With the release of Ekahau Site Survey version 8.5, two new visualizations were added to help characterize the RF spectrum environment. In order to gather spectrum data, an Ekahau Spectrum Analyzer dongle is required and must be enabled prior to the survey. Only one band (2.4 or 5 GHz) can be scanned per spectrum analyzer, if both bands are required to be scanned simultaneously then two spectrum analyzers would be required.

Spectrum Channel Power

The Spectrum Channel Power visualization shows the average total energy for a channel as measured by a spectrum analyzer. The energy includes both Wi-Fi and non-Wi-Fi signals.

In other words, how “loud” the transmissions in the spectrum were during the survey. The power can be originating from either Wi-Fi radios, or from other devices in the same frequency range. In most production networks, much of the channel power is caused by Wi-Fi signals. However, there are cases where non-Wi-Fi devices may transmit on the same frequency as Wi-Fi networks. For example, leaky microwave ovens are known to emit high powered signals across the 2.4 GHz band causing interference and disconnects for the nearby Wi-Fi networks. In addition to microwave ovens there are numerous other intentional and unintentional emitters that may transmit on the Wi-Fi frequency bands, such as Bluetooth devices, A/V equipment, RADAR, electrical motors, florescent lighting, and more.

If the survey is performed on a Greenfield environment (i.e. no Wi-Fi networks) and spectrum channel power is detected then it is likely there is a non-Wi-Fi device emitting in that area. It would be recommended that you therefore avoid the channel that is occupied when designing the new Wi-Fi network to minimize interference.

Spectrum Utilization

The Spectrum Utilization visualization shows the share of the time the spectrum power measured by the spectrum analyzer is high enough so that the channel can be considered as occupied.

This heatmap shows how crowded (i.e. percentage of time) the frequency was during the survey – taking into account both utilization caused by Wi-Fi, as well as other interferers. Typically, most of the utilization is originating from Wi-Fi networks, but it’s not uncommon to find interferers eating up most of the airtime as well.

Some interferers such as microwave ovens, jammers, and any device that constantly emits will take up a majority of the airtime. Wi-Fi networks on the other hand are often considered “polite” with regards to airtime fairness. The 802.11 standard is designed to allow devices to take turns using the frequency space, while other RF technologies have no such restrictions. Because of this inherent nature of Wi-Fi devices if non-Wi-Fi devices are utilizing the same frequency more often, then the Wi-Fi network performance will degrade causing slowdowns and disconnects.

Visualization Options

By default, the spectrum visualizations show the value for the maximum spectrum channel power or spectrum utilization over all channels at any point on the map. You can view per-channel as well from the Visualization Options menu as shown below:

Survey Inspector

With the addition of the two new visualizations and Real-Time Frequency Monitor (RTFM) in ESS version 8.5, the survey inspector tool has been updated. The spectrum heatmaps will provide a high level view of the spectrum environment, while the survey inspector is useful in providing detailed information about a particular location on the map.

It is important to understand that radio signals can change dramatically based on location and time, not all signals are continuous or widespread. To drill down into the spectrum at a particular location use the survey inspector tool by double clicking on the map at a measured survey point. The screenshot below shows the use of the survey inspector on a surveyed map with the heatmap on the top and the spectrum charts for the selected area on the bottom. The location selected is illustrated as an orange circle on the floor plan, in this case you can see the current location towards the top-left of the image.

These two new Spectrum visualizations will help identify pitfalls related to the RF spectrum that may otherwise go unnoticed if only a Wi-Fi survey was performed. By gathering data on the spectrum environment you can accurately identify potential interference sources and the channels they operate on such that you can avoid designing Wi-Fi networks that operate on those frequencies and troubleshoot existing issues.

Ekahau Site Survey version 8.5 has just been released with a couple of exciting new features and lots of smaller improvements and fixes. Watch Amanda introduce the main new features, Spectrum Analyzer integration and the Custom Notes tool: The new version brings: Spectrum Analyzer Integration Support for 1-2 Ekahau Spectrum Analyzers while surveying Real-Time Frequency Monitor view... Read more ›

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We also had the pleasure of meeting Chuck Lukaszewski from Aruba Networks at the CWNP conference. Chuck shares his expert insights on high density deployments, covering, for example, total system throughput, DFS channels and the myth of spatial reuse.

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